Insert for a tool for assembling a bone anchoring device and tool for assembling a bone anchoring device

ABSTRACT

An insert for a tool for assembling a bone anchoring device including a bone anchoring element with a head and a shaft to be anchored in bone and a receiving part, the insert configured for insertion into a holder of the tool, the insert including an elongate body with a longitudinal axis, wherein a first recess configured to receive a shaft of a bone anchoring element extends on a surface of the elongate body along the longitudinal axis, has a first diameter, and is oriented towards a first radial direction relative to the longitudinal axis, wherein a second recess configured to receive a shaft of a bone anchoring element extends on a surface of the elongate body along the longitudinal axis, has a second diameter greater than the first diameter, and is oriented towards a second radial direction relative to the longitudinal axis different than the first radial direction.

CROSS-REFERENCE TO RELATED APPLICATION(S)

The present application claims the benefit of U.S. Provisional PatentApplication Ser. No. 61/525,090, filed Aug. 18, 2011, the contents ofwhich are hereby incorporated by reference in their entirety, and claimspriority to European Patent Application EP 11 178 036.7, filed Aug. 18,2011 and Japanese Patent Application JP 2011-102944, filed May 2, 2011the contents of which are hereby incorporated by reference in theirentirety.

BACKGROUND

1. Field of the Invention

The invention relates to an insert for a tool for assembling a boneanchoring device including a bone anchoring element with a head and ashaft to be anchored in bone and a receiving part, and the tool forassembling such a bone anchoring device. The insert is configured to beinserted into a longitudinal recess of a holder of the tool. The insertis capable of receiving the bone anchoring element, and has at least tworecesses configured to receive different sized bone anchoring elements.

2. Description of Related Art

WO 2007/038350 A2 discloses an apparatus for connecting a bone anchor toa support rod, the apparatus including a connector body and a cap. Theconnector body has a socket for insertion, angulation and removal of abone anchor. A sleeve is provided, which is configured to fit over theconnector body in a temporary position, in which the sleeve permitsinsertion of the bone anchor, to move to a provisional locking positionin which the sleeve permits angulation but prevents removal of the boneanchor, and to move to a locking position, in which the sleeve preventsboth angulation and removal of the bone anchor.

SUMMARY

If a head of an anchoring element is freely pivotable with respect to areceiving part, alignment of the receiving part and insertion of a rodmay be difficult in more complex clinical applications, for example,when multiple bone anchors are to be connected to the rod.

In some instances, there is also a need to have a choice betweendifferent anchoring elements during surgery, to select the mostappropriate anchoring elements for a specific clinical application.

It is an object of the invention to provide an improved insert for atool for assembling a bone anchoring device and to provide an improvedtool for assembly of such a bone anchoring device.

A receiving part to be used with the tool according to an embodiment ofthe invention allows insertion of a head of a bone anchoring elementinto a receiving part body when a locking ring is in a first positionwhich is an insertion position. In this position, the locking ring islatched with respect to the receiving part body. Therefore, the lockingring will not be inadvertently moved to compress a head receivingportion of the receiving part body, in order to facilitate the insertionof the head.

In a second position, which is a pre-locking position, the locking ringis latched with respect to the receiving part body, and the headreceiving portion is compressed so that the bone anchoring element isheld in an adjustable angular position but is not fully locked. Thisprevents inadvertent removal of the bone anchoring element and holds thereceiving part body in an adjustable angular position with respect tothe head of the bone anchoring element. Therefore, safe and convenienthandling of the bone anchoring device during surgery can be assured.

In a third position, which is a locking position, the locking ringcompresses the head receiving portion such that the bone anchoringelement is fully locked and cannot pivot.

The receiving part body and the locking ring may be preassembled, andmay be delivered after manufacture in a configuration in which thelocking ring is latched in the first position to allow introduction ofthe head of the bone anchoring element. A suitable bone anchoringelement, for example, a bone screw with a desired diameter and length,can be selected and inserted into the receiving part. Thereafter, thelocking ring can be moved into the second position with respect to thereceiving part, where the head is pre-locked. The latching of thelocking ring in the receiving part body in the second position may beaudible, so that a person who assembles the bone anchoring device can besure of correct assembly of the bone anchoring element in the receivingpart. In the pre-locked condition, the bone anchoring element may onlybe pivotable with respect to the receiving part by applying anadditional force, to overcome the frictional force of the clamping ofthe head.

With such a bone anchoring device, a modular system can be provided,which allows for combinations of various anchoring elements with anysuitable receiving part on demand, depending on the actual clinicalrequirements. This reduces the costs associated with polyaxial screws,reduces inventory, and gives the surgeon a wide choice of implants.

A method of assembling the bone anchoring device according toembodiments of the invention can be carried out by any specialist, forexample, by a surgeon or any personnel assisting him or her before orduring surgery.

A tool and an insert according to embodiments of the invention is easyto handle and provides for safer assembly of the bone anchoring device.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and advantages of the invention will become apparentfrom the description of embodiments by means of the accompanyingdrawings. In the drawings:

FIG. 1 shows a perspective exploded view of a bone anchoring deviceaccording to an embodiment of the invention;

FIG. 2 shows a perspective view of the bone anchoring device of FIG. 1in an assembled state;

FIG. 3 shows an enlarged perspective view of a locking ring according toan embodiment of the invention;

FIG. 4 shows a cross-sectional view of the locking ring shown in FIG. 3along line A-A in FIG. 3;

FIG. 5 shows a cross-sectional view of a bone anchoring device accordingto an embodiment of the invention in an assembled state, the sectionbeing taken perpendicular to a rod axis, where the locking ring is in afirst position and is latched with respect to the receiving part body;

FIG. 6 shows a cross-sectional view of the bone anchoring device in anassembled state, the section being taken in a plane perpendicular to therod axis, where the locking ring is in a second position and is latchedwith respect to the receiving part body;

FIG. 7 shows a cross-sectional view of the bone anchoring device in anassembled state, with a rod inserted and fixed, the section being takenin a plane perpendicular to the rod axis, and wherein the locking ringis in a third position;

FIG. 8 shows a cross-sectional view of a portion of the bone anchoringdevice in a first step of assembly, where a bone anchoring element isgoing to be inserted into the receiving part;

FIG. 9 shows a cross-sectional view of a portion of the bone anchoringdevice in a second step of assembly, where a head of the bone anchoringelement has been introduced into the receiving part and is pre-locked;

FIG. 10 shows a cross-sectional view of a portion of the bone anchoringdevice where the head is locked;

FIG. 11 shows an enlarged cross-sectional view of a portion of thereceiving part, where the locking ring is in the first position and islatched with respect to the receiving part body to allow forintroduction of the head;

FIG. 12 shows an enlarged cross-sectional view of a portion of the boneanchoring device in a final locked state where additional clamping iseffected by means of the locking ring;

FIG. 13 shows a perspective view of a tool for assembling a boneanchoring device according to a first embodiment of the invention;

FIG. 14 shows an enlarged perspective view of a portion of the toolaccording to the first embodiment, with a bone anchoring elementinserted into a holder;

FIG. 15 shows a perspective view of a portion of the tool according tothe first embodiment, with a receiving part to be inserted into aholder;

FIG. 16 shows a perspective view of a portion of the tool according tothe first embodiment, with the receiving part introduced into theholder;

FIG. 17a shows a perspective view of the tool according to the firstembodiment depicting a step of assembly, where the head of the boneanchoring element is going to be inserted into the receiving part;

FIG. 17b shows an enlarged view of a portion of FIG. 17 a;

FIG. 18a shows a perspective view of the tool according to the firstembodiment depicting another step of assembly, with the head of the boneanchoring element inserted into the receiving part;

FIG. 18b shows an enlarged portion of FIG. 18 a;

FIG. 19 shows an enlarged perspective view of a portion of the toolaccording to the first embodiment with the bone anchoring device afterinsertion of the head and before entering the pre-locking position;

FIG. 20 shows a perspective view of the tool according to the firstembodiment with the bone anchoring device in the pre-locking position;

FIG. 21 shows a perspective view of an enlarged portion of the toolaccording to the first embodiment, where the locking ring of the boneanchoring device has assumed the pre-locking position and clamps thehead;

FIG. 22 shows a perspective view of a tool for assembling the boneanchoring device according to a second embodiment of the invention;

FIG. 23 shows a perspective view of a second holder according to thesecond embodiment;

FIG. 24 shows a perspective exploded view of the second holder accordingto the second embodiment;

FIG. 25a shows a cross-sectional view of the second holder in a firstposition according to the second embodiment;

FIG. 25b shows a cross-sectional view of the second holder in a secondposition according to the second embodiment;

FIG. 26a shows a perspective view of a portion of the tool in a firstposition of use according to the second embodiment;

FIG. 26b shows a perspective view of a portion of the tool in a secondposition of use according to the second embodiment;

FIG. 26c shows a perspective view of a portion of the tool in a thirdposition of use according to the second embodiment;

FIG. 27 shows a cross-sectional view of a portion of the tool accordingto the second embodiment in the first position of use;

FIG. 28a shows a cross-sectional view of an enlarged portion of the toolin the first position of use according to the second embodiment;

FIG. 28b shows a cross-sectional view of an enlarged portion of the toolin the second position of use according to the second embodiment;

FIG. 28c shows a cross-sectional view of an enlarged portion of the toolin the third position of use according to the second embodiment;

FIG. 29 shows a perspective view of a tool according to a thirdembodiment of the invention, depicting a step of assembly where the headof the bone anchoring element is to be inserted into the receiving part;

FIG. 30a shows a perspective view of an insert for a first holderaccording to the third embodiment, in the form of a cylindrical sectionhaving several cylinder-shaped or U-shaped recesses;

FIG. 30b shows a perspective view of a first holder according to thethird embodiment;

FIG. 31 shows the first holder and the insert in an assembled stateaccording to the third embodiment;

FIG. 32 shows a cross-sectional view of the insert according to thethird embodiment;

FIG. 33 shows a cross-sectional view of a frame, the first holder, andthe insert, the assembly holding a screw according to the thirdembodiment;

FIG. 34 shows a perspective view of a tool according to a fourthembodiment of the invention, depicting a step of assembly where a headof a bone anchoring element is to be inserted into a receiving part;

FIG. 35 shows a perspective view of an insert and a first holderaccording to the fourth embodiment prior to assembly;

FIG. 36 shows a perspective view of the insert and the first holderaccording to the fourth embodiment in an assembled state;

FIG. 37 shows a perspective top view of the first holder according tothe fourth embodiment;

FIG. 38 shows a perspective bottom view of the first holder according tothe fourth embodiment;

FIG. 39 shows a top view of the first holder according to the fourthembodiment;

FIG. 40 shows a side view of the first holder according to the fourthembodiment;

FIG. 41 shows another side view of the first holder according to thefourth embodiment;

FIG. 42 shows a perspective view of the insert according to the fourthembodiment in a first position;

FIG. 43 shows a perspective view of the insert according to the fourthembodiment in a second position;

FIG. 44 shows a top view of the insert according to the fourthembodiment;

FIG. 45 shows a side view of the insert according to the fourthembodiment;

FIG. 46 shows a cross-sectional view of a frame, the first holder, andthe insert in a first position, the assembly holding a screw accordingto the fourth embodiment; and

FIG. 47 shows a cross-sectional view of the frame, the first holder, andthe insert in a second position, the assembly holding a screw accordingto the fourth embodiment.

DETAILED DESCRIPTION

As shown in FIGS. 1 to 7, a bone anchoring device according to anembodiment of the invention includes a bone anchoring element 1 in theform of a bone screw having a threaded shaft 2 and a head 3 with acurved surface portion. In this embodiment the head 3 is sphericalsegment-shaped. The head 3 has a recess 4 for engagement with a tool.The bone anchoring device also includes a receiving part body 5 forreceiving a rod 6 to connect it to the bone anchoring element 1.Further, a fixation element 7 in the form of an inner screw is providedfor fixing the rod 6 in the receiving part body 5. The bone anchoringdevice also includes a locking ring 8 for locking the head 3 in thereceiving part body 5.

The receiving part body 5 includes a rod receiving portion 9, which issubstantially cylindrical and which has a first end 9 a and a second end9 b opposite the first end 9 a. A coaxial first bore 10 is provided atthe second end 9 b, as shown in FIGS. 5 to 7. A diameter of the firstbore 10 is smaller than a diameter of the head 3 of the bone anchoringelement 1. The rod receiving portion 9 further has a coaxial second bore11 extending from the first end 9 a to a distance from the second end 9b. A diameter of the second bore 11 is larger than that of the firstbore 10. A substantially U-shaped recess 12 extends from the first end 9a in the direction of the second end 9 b in the rod receiving portion 9,a diameter of the recess 12 being slightly larger than a diameter of therod 6 in such a way that the rod 6 can be placed in the recess 12 andcan be guided therein. By means of the recess 12, two free legs 12 a, 12b are formed on which an internal thread 13 is provided. The internalthread 13 can be a metric thread, a flat thread, a negative anglethread, a saw-tooth thread, or any other type of thread. Preferably, athread such as a flat thread or negative angle thread is used, whichprevents splaying of the legs 12 a, 12 b when the inner screw 7 isscrewed-in. The depth of the recess 12 is such that the rod 6 and theinner screw 7 can be inserted between the legs 12 a and 12 b.

As can be seen in FIG. 1, cut-outs 15 are provided in the rod receivingportion 9 on either end of the channel formed by the recess 12.

On an outer surface of the rod receiving portion 9, in the region of thelegs 12 a, 12 b, a groove 16 is provided, which extends in acircumferential direction and serves for engagement with a portion ofthe locking ring 8. The groove 16 is asymmetric in such a way that itallows for disengagement between the locking ring 8 and the groove 16when the locking ring 8 is shifted in one direction. The asymmetricshape of the groove 16 is realized by a downwardly inclined lower wall16 a and an upper wall 16 b that is substantially perpendicular to anouter surface of the rod receiving portion 9.

At the side of the second end 9 b the receiving part body 5 has a headreceiving portion 17 providing an accommodation space for the head 3 ofthe bone anchoring element 1. A largest outer diameter of the headreceiving portion 17 is smaller than a largest outer diameter of the rodreceiving portion 9. An internal hollow section 18 forms a seat for thehead 3 of the bone anchoring element 1, and is open via an opening 19 toa free end 17 b of the head receiving portion 17. The hollow section 18corresponds in its shape to the shape of the head 3. In the embodimentshown, the hollow section 18 is a spherical section to accommodate thespherical head 3. Furthermore, the hollow section 18 is configured toencompass the head 3 of the bone anchoring element 1 from the side,covering a region including the largest diameter of the head 3.

A plurality of slits 20 are provided in the head receiving portion 17,which are open to the free end 17 b. The slits 20 make the headreceiving portion 17 flexible so that it can be compressed to clamp andfinally lock the head 3 in the hollow internal portion 18 by means offriction. The number and size of slits 20 is provided depending on thedesired flexibility of the head receiving portion 17. The flexibility ofthe head receiving portion 17 is such that the head 3 of the anchoringelement 1 can be inserted by expanding the head receiving portion 17,and the head 3 can be clamped by compressing the head receiving portion17.

The outer surface of the head receiving portion 17 has a first section21, with an outer diameter which increases towards free end 17 b, forexample in an outwardly curved or conically widening manner. Adjacent tothe first section 21, there is a circumferential groove 22, which isrecessed with respect to the first section 21 and which serves forengagement with a corresponding portion of the locking ring 8. Thegroove 22 is asymmetric to allow for disengagement between the lockingring 8 and the groove 22 when moving the locking ring 8 in onedirection. The asymmetric shape of the groove 22 is realized by a lowerdownwardly inclined wall 22 a and an upper wall 22 b that issubstantially perpendicular to an outer surface of the head receivingportion 17.

Adjacent the groove 22 on a side opposite the first section 21, there isa third portion 23 of the head receiving portion 17 with a substantiallycylindrical outer surface. The third portion 23 is configured tocooperate with a portion of the locking ring 8 to enhance the clampingeffect of the locking ring 8.

The locking ring 8 will now be described with reference to FIGS. 1 to 7.The locking ring 8 is substantially cylindrical and has an upper end 8 aand a lower end 8 b. In the mounted state the upper end 8 a is orientedin the direction of the first end 9 a of the rod receiving portion 9,while the lower end 8 b is oriented towards the free end 17 b of thehead receiving portion 17. Near the lower end 8 b, a first portion 81with an inner surface 81 a is provided which cooperates with the firstouter surface portion 21 of the head receiving portion 17 to compressthe head receiving portion 17. The outer surface of the first portion 81may also be tapered to reduce an outer bottom diameter. The size of thefirst portion 81 is such that, for example, the tapered inner surface 81a can engage the outer surface portion 21 of the head receiving portion17 to exert a compression force onto the head receiving portion 17. Theinner surface 81 a of the first portion 81 of the locking ring 8 canalso be curved with a curvature directed towards a center of the lockingring 8.

At the lower end 8 b, the locking ring 8 includes an inwardly projectingedge 82, the inner diameter of which is smaller than the inner diameterof the other portions of the locking ring 8. The inwardly projectingedge 82 is configured to engage the groove 22 of the head receivingportion 17.

The locking ring 8 further has a third portion 83 with upwardlyextending wall portions 83 a, which are separated from each other byslits 84. The upwardly extending wall portions 83 a are arranged at anouter circumference of an inner circumferential shoulder 85 of thelocking ring 8, and render the third portion 83 of the locking ring 8flexible. The number and size of the slits 84 and the thickness of thewall portions 83 a are configured such that a desired flexibility isrealized. At the free ends of the wall portions 83 a are engagementsections 83 b which are shaped so as to engage the groove 16 provided onthe outer surface of the rod receiving portion 9. The inner diameter ofthe third portion 83 of the locking ring 8 is only slightly larger thanthe outer diameter of the rod receiving portion 9, as can be seen inFIG. 5.

The locking ring 8 is sized in such a way with respect to the headreceiving portion 17, that the head receiving portion 17 can expandwithin the locking ring 8 to allow the introduction of the head 3 whenthe locking ring 8 is in the first position, as shown in FIG. 5.

Two projections 86, which are located diametrically opposite to eachother, are formed in the third portion 83 of the locking ring 8. Theprojections 86 have a height where they extend into the cut-outs 15 andproject above the bottom of the substantially U-shaped recess 12 whenthe locking ring 8 is in a position in which the head 3 is not yetlocked, as shown in FIGS. 5 and 6. A free end surface 86 a of theprojections 86 can be curved, particularly inwardly curved, with acurvature corresponding to an outer surface of the rod 6. The lockingring 8 is arranged in such a manner around the head receiving portion 17of the receiving part body 5, that the projections 86 are located at thepositions of (e.g., are aligned with) the recess 12. Here, theprojections 86 prevent the locking ring 8 from rotating when the rod 6is not inserted.

The flexibility of the head receiving portion 17 and the size of thehead receiving portion 17 at the open end 17 b allows for mounting ofthe locking ring 8 by assembling the locking ring 8 from the free end 17b onto the head receiving portion 17. Since the outer diameter of thehead receiving portion 17 is smaller than that of the rod receivingportion 9, the locking ring 8 may only project minimally beyond the rodreceiving portion 9 in a radial direction.

The inner screw 7 has a thread corresponding to the internal thread 13provided on the legs 12 a, 12 b. If a thread, which prevents the legs 12a, 12 b from splaying is used, a single fixation element such as theinner screw 7 is sufficient. This reduces the size of the bone anchoringdevice in a radial direction. Other fixation elements such as, forexample, an outer nut are also possible.

The receiving part body 5, the locking ring 8, the inner screw 7 and thebone anchoring element 1 are made of bio-compatible materials, forexample, titanium or stainless steel or a bio-compatible alloy such asnitinol or a bio-compatible plastic material, such as polyether etherketone (PEEK). The parts can be made of the same or of differentmaterials.

The function of the locking ring 8 is now explained with referencedFIGS. 5 to 12. As shown in FIG. 5, the locking ring 8 is in a firstposition, which is an insertion position and where the locking ring 8 islatched with respect to the receiving part body 5. In the firstposition, the inwardly projecting edge 82 of the locking ring 8 engagesgroove 22 on the outer surface of the head receiving portion 17. As canbe seen in the figures, the inner diameter of the inwardly projectingedge 82 is larger than the outer diameter of the head receiving portion17 at the position of the groove 22, so as to allow for expansion of thehead receiving portion 17 when the head 3 is introduced. In the firstposition, the locking ring 8 is additionally held by a clamping forcebetween the rod receiving portion 9 of the receiving part body 5 and theflexible wall portions 83 a of the locking ring 8, which are slightlybent outwards, as can be seen in particular in FIGS. 5, 8, and 11.

When the locking ring 8 is in the first position, the head receivingportion 17 is not compressed. In this position, the introduction of thescrew head 3 is possible as can be seen in FIG. 8. In the firstposition, the locking ring 8 is prevented from moving upwards towardsthe first end 9 a of the rod receiving portion 9, since the shoulder 85of the locking ring 8 abuts against the second end 9 b of the rodreceiving portion 9, while the inwardly projecting edge 82 of thelocking ring 8 abuts against the upper wall 22 b of groove 22. As shownin particular in FIG. 8, the abutment of the locking ring 8 against thesecond end 9 b and against the upper wall of groove 22 holds the lockingring 8 in place against upward movement. The inclined lower wall 22 a ofthe groove 22 prevents inadvertent downward movement of the locking ring8 but allows downward movement of the locking ring 8, upon exertion ofan additional force. Since portions of the inner diameter of the lockingring 8 are larger than corresponding portions of the outer diameter ofthe head receiving portion 17 in a non-compressed state in the firstposition, an expansion of the head receiving portion 17 into a spacebetween the locking ring 8 and the head receiving portion 17 ispossible. In addition, in the first position, the head 3 can freelypivot,

FIGS. 6 and 9 illustrate the bone anchoring device in a second positionin which the locking ring 8 is latched with respect to the receivingpart body 5 in a pre-locking position. In the second position, thelocking ring 8 has been shifted from the first position towards the freeend 17 b of the head receiving portion 17 until the engagement portions83 b of the flexible wall portions 83 a resiliently snap into the groove16 provided on the rod receiving portion 9. Once in the second position,the free upper edge of the engagement portions 83 b will abut againstthe upper wall 16 b of the groove 16, as shown in FIGS. 6 and 9, therebypreventing upward movement of the locking ring 8 out of the pre-lockingposition. On the other hand, the inclined lower wall surface 16 a of thegroove 16 prevents inadvertent downward movement of the locking ring 8towards the free end 17 b, but allows for downward movement uponexertion of an additional force.

In the second position, as can be seen in particular in FIGS. 6 and 9,the inner inclined surface 81 a of the locking ring 8 presses againstthe first outer surface portion 21 of the head receiving portion 17, soas to compress the head receiving portion 17 to clamp the head 3 withinthe hollow internal portion 18 without fully locking the head 3. Inaddition, the inwardly projecting edge 82 of the locking ring 8 pressesagainst the third portion 23 of the head receiving portion 17, resultingin an additional clamping force. Therefore, clamping of the head 3 canbe effected not only from above and/or the sides of the head 3, but alsofrom a region around the lower portion of head 3. Pre-locking means thatunder conditions arising during surgery, the angular position of thebone anchoring element 1 with respect to the receiving part body 5 ismaintained, and can be loosened only by exerting an additional forceonto the receiving part body 5 and/or the bone anchoring element 1 ofthe bone anchoring device. In the pre-locked position, the boneanchoring element 1 cannot be removed from the receiving part 5. Hence,accidental or inadvertent removal of the head 3 is not possible.However, angulation of the bone anchoring device to be adjusted to adesired angle is still possible, for example, by manual adjustment.

A third position, which is the locking position, is shown in FIGS. 7,10, and 12. The third position is defined as a position in which thescrew head 3 is finally locked within the head receiving portion 17. Theinner surface 81 a of the locking ring 8 engages the outer surface ofthe first portion 21 of the head receiving portion 17 in such a way thatthe head 3 is locked by compression of the head receiving portion 17. Inaddition, the inwardly projecting edge 82 of the locking ring 8 furthercompresses the head receiving portion 17 at the third portion 23,thereby enhancing the locking force.

The dimensions of the receiving part body 5 and the locking ring 8 areconfigured such that desired clamping forces can be achieved in thesecond position and in the third position, respectively.

The third position can be reached by shifting the locking ring 8relative to the receiving part body 5 such that the engagement portions83 b and the inwardly projecting ring 82 slide along the lower inclinedwall portions 16 a and 22 a of the grooves 16, 22, respectively.

The bone anchoring device is preassembled as follows. First, the lockingring 8 is mounted onto the receiving part body 5 from the free end 17 b.This can be done, for example, by the manufacturer. Preferably, thelocking ring 8 is in the first position, where it is latched byengagement or alignment of the inwardly projecting edge 82 with thegroove 22.

Thereafter, the head 3 of the anchoring element 1 can be introduced fromthe free end 17 b into the hollow internal portion 18 of the headreceiving portion 17. Thereafter, the locking ring 8 is moved downwardsrelative to the receiving part body 5, so that the inwardly projectingring 82 slides out of the groove 22 and the engagement portions 83 b ofthe flexible wall portions 83 a snap into groove 16, to reach the secondposition, in which the head 3 is pre-locked by frictional clamping.

A tool for assembling the bone anchoring device and its operationaccording to a first embodiment will now be described with reference toFIGS. 13 to 21. The tool 100 includes a frame 101 with a first holder102 for the bone anchoring element 1 and a second holder 103 for thereceiving part (including, for example, the receiving part body 5 andthe locking ring 8). The holders 102, 103 are oriented such that alongitudinal axis of the bone anchoring element 1 is horizontal orparallel with respect to a surface on which the tool is placed orpositioned. The first holder 102 has a recess 102 a for the shank 2 ofthe bone anchoring element 1, which serves for holding and guiding theshank 2. The diameter of the recess 102 a is smaller than the diameterof the head 3 in at least an area of a free end of the first holder 102facing the second holder 103. Therefore, a free end surface 102 b of thefirst holder 102 serves as an abutment for the head 3 of the boneanchoring element 1. The first holder 102 is supported on the frame 101.

The second holder 103 for the receiving part is also supported on theframe 101. It has a substantially circular recess 103 a foraccommodating a portion of the receiving part. The orientation of thesecond holder 103 with respect to the first holder 102 is such that acentral axis of the receiving part is configured to be positionedcoaxial with the axis of the bone anchoring element 1 when the receivingpart and the bone anchoring element 1 are both inserted into theirrespective holders 102, 103. The circular recess 103 a can be adjustedto have two different depths. This may be realized by an insert 104which is inserted in a corresponding slot provided in the second holder103 and which can be shifted in a direction transverse to the directionof the central axis of the recess 103 a, to limit the depth of recess103 a. The insert 104 has one circular recess 142. In position 1, asshown in FIGS. 13 to 18, the insert limits the depth of the recess 103 ato a first depth 141, and thus provides an abutment for the first end 9a of the receiving part body 5. In position 2, which is shown in FIGS.19 to 21, the insert 104 is shifted such that its recess 142 forms ordefines the bottom of the recess 103 a of the second holder 103, thedepth of which is greater than the depth 141 of the recess 103 a whenthe insert 104 is in the first position. As such, the recess 142effectively increases the length of the recess 103 a. The receiving partcan therefore be inserted deeper into the recess 103 a until an outersurface 103 b of the second holder 103 forms an abutment for the lockingring 8, as shown in FIGS. 19 to 21. The shape of the recess 103 a neednot be circular, but can be otherwise shaped, and in particular, it canbe adapted to correspond to the contour of the receiving part.

The first holder 102 for the bone anchoring element 1 is movablerelative to the second holder 103 for the receiving part body 5 in anaxial direction. The first holder 102 can be actuated via a lever 105and a handle 106. It is to be understood that the lever 105 is only anexample, and that movement of the first holder 102 for the boneanchoring element 1 can be effected in many other ways, for example, bymeans of a toothed rack.

The dimensions of the tool 100 are configured such that, by movement ofthe first holder 102 for the bone anchoring element 1 with respect tothe second holder 103 in which a receiving part is inserted, asufficient force can be exerted to introduce the head 3 of the boneanchoring element 1 into the head receiving portion 17, when the recess103 a is set to have the first depth 141 and the locking ring 8 is inthe first position. It is further configured such that a sufficientforce can be exerted onto the locking ring 8 when first holder 102 ismoved again relative to the second holder 103 to move the locking ring 8out of the first position into the second position, when the recess 103a is set to have the second depth 142.

The operation of the tool according to the first embodiment is shown inFIGS. 17 to 21. As shown in FIGS. 17a and 17b first, the bone anchoringelement 1 is inserted into the first holder 102 and the receiving partbody 5, with mounted locking ring 8 in the first position, is mounted inthe recess 103 a of the second holder 103 when the recess 103 a is setto have the first depth 141.

In a next step, as shown in FIGS. 18a and 18b , the handle 106 isactuated to actuate the lever 105 so that screw head 3 is pushed intothe hollow internal portion 18 of the head receiving portion 17. Thebottom of the recess 103 a of the second holder 103 serves as anabutment for the receiving part, so that the head receiving portion 17can expand to allow the introduction of the head 3. The handle 106 isactuated until the head 3 of the bone anchoring element 1 is latched orinserted in the hollow internal portion 18. The latching may produce anaudible sound.

Thereafter, as shown in FIGS. 19 to 21, the first holder 102 for thebone anchoring element 1 is shifted backward and the insert 104 is movedto the second position, in which the circular recess 142 forms ordefines the bottom of recess 103 a to provide and use outer surface 103b of holder 103 as an abutment for the locking ring 8.

As shown in FIGS. 20 and 21, the handle 106 is then actuated to push thefirst holder 102 towards the second holder 103. By means of this, thehead 3 with the receiving part body 5 is pushed farther into the bottomof the recess 103 a, which has a depth where the free front surface 103b of the second holder 103 presses against the engagement portions 83 bof the flexible wall portions 83 a of the locking ring 8, thereby movingthe locking ring 8 out of the first position into the second position,where the engagement portions 83 b are latched in the groove 16 on therod receiving portion 9. When the engagement portions 83 b snap into thegroove 16, the latching of the locking ring 8 with respect to thereceiving part body 5 may be audible, which indicates that the correctpre-locking position is reached.

Thereafter, the first holder 102 is moved backward and the boneanchoring device is removed.

A tool for assembling the bone anchoring device and its operationaccording to a second embodiment will now be described with reference toFIGS. 22 to 28 c. As can be seen from FIG. 22, the tool 200 includes aframe 201 with a first holder 202 for the bone anchoring element 1 and asecond holder 203 for the receiving part (again including, for example,the receiving part body 5 and the locking ring 8). The tool 200according to the second embodiment only differs from the tool 100according to the first embodiment in that the second holder 203 isdifferent from the second holder 103 according to the first embodiment.The holders 202, 203 may be oriented such that a longitudinal axis ofthe bone anchoring element 1 is horizontal or parallel with respect to asurface on which the tool is placed or positioned. The holder 202 has arecess 202 a for the shank 2 of the bone anchoring element 1, whichserves for holding and guiding the shank 2. The diameter of the recess202 a is smaller than the diameter of the head 3 in at least an area ofa free end of the first holder 202 facing the second holder 203.Therefore, a free end surface 202 b of the first holder 202 serves as anabutment for the head 3 of the bone anchoring element 1. The firstholder 202 is supported on the frame 201.

The second holder 203 for the receiving part is also supported on theframe 201. The orientation of the second holder 203 with respect to thefirst holder 202 is such that a central axis of the receiving part isconfigured to be positioned coaxial with the axis of the bone anchoringelement 1 when the receiving part and the bone anchoring element 1 areboth inserted into their respective holders 202, 203.

The first holder 202 for the bone anchoring element 1 is movablerelative to the second holder 203 for the receiving part body 5 in anaxial direction. The first holder 202 can be actuated via a lever 205and a handle 206. It is to be understood that the lever 205 is only anexample, and that movement of the first holder 202 for the boneanchoring element 1 can be effected in many other ways, for example, bymeans of a toothed rack.

As can be seen from FIG. 23, the second holder 203 includes a main body210, a first end 211, a second end 212, a bore 220, and a substantiallycircular recess 203 a for accommodating a portion of the receiving part.As can be seen from FIG. 24 the second holder 203 further includes athread 213, a sleeve 214, a spring 215, a plate 216 and a screw 217. Ascan be seen from FIGS. 25a and 25b , the cup-shaped sleeve 214 is closedon a side extending towards the first end 211 and is configured to slidewithin the bore 220 of the main body 210 since its diameter is slightlysmaller than the inner diameter of at least a portion of the bore 220.The spring 215 is provided within the sleeve 214 and is supported by theplate 216 and the inner screw 217 which is screwed into the thread 213of the main body 210. Other designs for supporting the spring 215 arepossible, such as for example, a base which is press-fitted into thesecond holder 203. The spring 215 is shown as a helical spring 215 inthe second embodiment. However other spring elements are possible, suchas leaf springs, disk springs, elastomer cushions, etc.

The circular recess 203 a can have varying depths. This is realized bythe movable sleeve 214 which provides an abutment for the receivingpart. In FIG. 25a a first abutment position and in FIG. 25b a secondabutment position are shown, where a space 218 is shown in FIG. 25b whenthe spring 215 is compressed. The sleeve 214 provides an abutment forthe first end 9 a (see FIG. 1) of the receiving part body 5. In thefirst abutment position, the closed side of the sleeve 214 forms thebottom of the recess 203 a of the second holder 203, the depth of whichis less than a depth of the recess 203 a in the second abutment positionthat is achieved when a greater force is applied by the first end 9 a ofthe receiving part onto the sleeve 214 and the spring 215, respectively.The force is exerted by the handle 206 and the lever 205 via the firstholder 202, the shaft 2 and the head 3 to the first end 9 a of thereceiving part and then to the sleeve 214. The shape of the recess 203 aneed not be circular, but can be otherwise shaped, and in particular, itcan be adapted to correspond to any possible contour of the receivingpart.

The dimensions of the tool 200 and the spring force are configured suchthat, by means of moving the first holder 202 with the bone anchoringelement 1 relative to the second holder 203 in which a receiving part isinserted, a first force can be exerted to introduce the head 3 of thebone anchoring element 1 into the head receiving portion 17, when therecess 203 a is set to have the first depth and the locking ring 8 is inthe first position. It is further configured such that a second forcecan be exerted onto the locking ring 8 when the first holder 202 ismoved closer relative to the second holder 203 to move the locking ring8 out of the first position into the second position, where the recess203 a has the second depth. The tool 200 according to the secondembodiment of the invention allows for mounting of various boneanchoring devices with, for example, receiving parts having differentheights and/or various different locking ring positions relative to thereceiving part.

The operation of the tool according to the second embodiment is shown inFIGS. 26a to 28c . As shown in FIGS. 26a , 27 and 28 a first, the boneanchoring element 1 is inserted into the first holder 202 and thereceiving part body 5, with mounted locking ring 8 in the firstposition, is mounted in the recess 203 a of the second holder 203 whenthe recess is set to have the first depth.

In a next step, as shown in FIGS. 26b and 28b , the handle 206 isactuated to actuate the lever 205 (see FIG. 22) so that the screw head 3is pushed into the hollow internal portion 18 (see FIG. 5) of the headreceiving portion 17. The bottom of the recess 203 a of the secondholder 203, i.e. the sleeve 214, serves as an abutment for the receivingpart, so that the head receiving portion 17 can expand to allow theintroduction of the head 3. The handle 206 is actuated until the head 3of the bone anchoring element 1 is latched or inserted in the hollowinternal portion 18. The latching may produce an audible sound. Thelocking ring 8 may not yet contact a side wall of the first end 211. Thecounterforce of the spring 215 is greater than the counterforce frominsertion of the head 3 into the receiving part body 5. Therefore, thespring 215 is not compressed during this step.

As shown in FIGS. 26c and 28c , the handle 206 is then actuated furtherto push the first holder 202 closer to the second holder 203. By meansof this, the head 3 with the receiving part body 5 is pushed against thebottom of the recess 203 a, i.e. the sleeve 214. The force which isneeded for moving the locking ring 8 and the receiving part body 5relative to each other is greater than the counterforce from the spring215. Therefore, the spring 215 is compressed. The recess 203 a now has adepth where the side wall of the first end 211 of the second holder 203presses against the engagement portions 83 b of the flexible wallportions 83 a of the locking ring 8 (see FIG. 3), thereby moving thelocking ring 8 out of the first position into the second position, wherethe engagement portions 83 b are latched in the groove 16 on the rodreceiving portion 9. When the engagement portions 83 b snap into thegroove 16, the latching of the locking ring 8 with respect to thereceiving part body 5 may be audible, which may indicate that thecorrect pre-locking position is reached.

Thereafter, the first holder 202 is moved backward and the boneanchoring device is removed. One advantage of the second embodiment ofthe tool 200 as compared to the first embodiment of the tool 100 is thatonly a singe actuation of the handle 206 is needed, and no additionalparts have to be moved during the mounting of the bone anchoring device.

By means of the tool 200 according to the second embodiment, assembly ofthe bone anchoring device can be easily completed in one step, includingthe introduction of the head and the mounting of the bone anchoringdevice into the pre-lock position.

A third embodiment of a first holder 302 for the bone anchoring elementwill now be described with reference to FIGS. 29 to 33. The tool 300shown in FIG. 29 can be the same as the tool 100 or 200 described above,or have similar features, except for the first holder 302, whichreplaces the first holders in the previous embodiments.

The first holder 302, shown in FIGS. 30b and 31, has a longitudinalU-shaped recess 302 a which referring to FIG. 30b , extends from one endtowards another end in a longitudinal direction and from the side of thefirst holder 302 inwards. The diameter of the recess 302 a is smallerthan the diameter of a head 3 of a bone anchoring element 1. Therefore,a free end surface 302 b of the first holder 302 serves as an abutmentfor the head 3 of the bone anchoring element 1. The first holder 302 issupported on the frame 301.

FIG. 30a and FIG. 32 show an insert 320 according to a third embodimentfor the first holder in the form of a cylindrical section having aplurality of longitudinally extending recesses 322 a, 322 b, 322 c thatare arranged circumferentially around a central axis 323 of the insert320. The recesses are sized and/or adapted for the insertion of screwsor other bone anchoring elements with different shanks. h the embodimentshown the insert 320 has a first cylinder-shaped or U-shaped recess 322a having a first radius, a second cylinder-shaped or U-shaped recess 322b having a second radius, and a third cylinder-shaped or U-shaped recess322 c having a third radius, where the three radii may be different fromeach other. The three recesses 322 a, 322 b, 322 c may extend the lengthof the insert 320, as can be seen from FIG. 30a . The insert 320 has afirst end and a second end, wherein a first pin 321 a is provided on thefirst end and a second pin 321 b is provided on the second end. The pins321 a, 321 b are in line with the central axis 323 of the insert 320.

Referring to FIG. 30b , the first holder 302 has a first end and asecond end, where on the first end a first slot 311 is provided and nearthe second end a second slot 312 is provided which both extend from aside of the first holder 302 inwards. The second end of the first holder302 is configured to be connected to a lever 305 and a handle 306 of thetool 300, as can be seen in FIG. 29.

The U-shaped recess 302 a of the first holder 302 is provided forreceiving the insert 320. The radius of the circular portion of theU-shaped recess 302 a may be substantially the same as the radius of theinsert 320.

As can be seen from FIG. 31, in a mounted state, the first pin 321 a ofthe insert 320 fits into the first slot 311 of the first holder 302, andthe second pin 321 b of the insert 320 fits into the second slot 312 ofthe first holder 302. The insert 320 is supported and guided by the pins321 a, 321 b, and is also held by the U-shaped recess 302 a of the firstholder 302, as can be seen in FIG. 33.

The orientation of the first holder 302 with respect to a second holder(e.g., second holder 103 or 203 as seen in the previous toolembodiments) is such that a central axis of a receiving part 5 isconfigured to be positioned coaxial with an axis of the bone anchoringelement 1 when the receiving part 5 is inserted into the second holderand the bone anchoring element 1 is inserted into the first holder 302in one of the recesses 322 a, 322 b or 322 c of the insert 320.

The three recesses 322 a, 322 b or 322 c are adapted to receivedifferent sized shanks of bone anchoring elements. With reference toFIGS. 29, 31, and 33, a particular recess 322 a, 322 b, 322 e which isin use will face outwards towards the opening of the U-shaped recess 302a. In this embodiment of the insert 320, mounting of at least threedifferent sized bone anchoring elements can be accommodated. Forchanging the recess 322 a, 322 b, 322 c which is in use, the insert 320can be rotated around its axis 323.

A fourth embodiment of a first holder 402 for the bone anchoring element1 will now be described with reference to FIGS. 34 to 47. The tool 400shown in FIG. 34 can be the same tool 200 or 300 described above, orhave similar features, except for the first holder 402 which replacesthe first holders in the previous embodiments.

The first holder 402, shown in FIGS. 34 to 41, has a longitudinalU-shaped recess 402 a which referring to, for example, FIG. 36, extendsfrom one end towards another end in a longitudinal direction and fromthe side of the first holder 402 inwards. The diameter of the recess 402a is smaller than the diameter of the head 3 of the bone anchoringelement 1 at at least an end of the first holder 402. Therefore, a freeend surface 402 b of the first holder 402 serves as an abutment for ahead 3 of a bone anchoring element 1 by means of a semicircular recess.The first holder 402 is supported on the frame 401. Furthermore,adjacent to the free end surface 402 b, a slot 423 perpendicular ortransverse to the U-shaped recess 402 a is provided that extends intothe recess 402 a. Referring to the illustration in FIG. 37, the slot 423intersects an upper region of the two legs of the U-shaped recess 402 a.

FIGS. 35 and 42 to 45 show an insert 420 for the first holder 402according to the fourth embodiment, in the form of a cylindrical sectionhaving a first longitudinally extending recess 422 a and a secondlongitudinally extending recess 422 b that are arranged on oppositesides of the insert 420. The recesses 422 a and 422 b are sized and/oradapted for insertion of screws or other bone anchoring elements 1 withdifferent shanks. In the embodiment shown, the first cylinder-shaped orU-shaped recess 422 a has a first radius, for example, for receiving 4-6mm shanks, and the second cylinder-shaped or U-shaped recess 422 b has asecond radius, for example for receiving 7-9 mm shanks. Other radiicombinations for the two recesses 422 a and 422 b are also possible. Therecesses 422 a and 422 b may extend the full length of the insert 420,as can be seen from FIGS. 35, 42-44.

The insert 420 has a first end and a second end, wherein a pin 424 isprovided on the first end that extends perpendicular or transverse tothe longitudinal recesses 422 a and 422 b. As can be seen from FIG. 42,the pin 424 has a spherical end portion and is provided on thecylindrical outer wall of the insert 420.

Referring to FIG. 37, the first holder 402 has a first end and a secondend, wherein on the first end a slot 411 is provided which extends froma side of the first holder 402 inwards. The second end of the firstholder 402 is configured to be connected to a lever 405 and a handle 406of the tool 400, as can be seen in FIG. 34.

The U-shaped recess 402 a of the first holder 402 is provided forreceiving the insert 420 (see FIG. 36). A radius of the circular portionof the U-shaped recess 402 a may be substantially the same as an outerradius of the insert 420. As can be seen from FIG. 36, in a mountedstate, the pin 424 of the insert 420 fits into the slot 423 of the firstholder 402, where the pin 424 may be received by the slot 423 in twopositions by rotating the insert 420, for example, by using the pin 424.The insert 420 is supported and guided by the U-shaped recess 402 a ofthe first holder 402, as can be seen in FIGS. 46 and 47.

An orientation of the first holder 402 with respect to the secondholder, such as second holder 103 or 203, is such that a central axis ofa receiving part 5 is configured to be positioned coaxial with an axisof a bone anchoring element 1 when the receiving part 5 is inserted intothe second holder and the bone anchoring element 1 is inserted into thefirst holder 402 in one of the recesses 422 a or 422 b of the insert420.

The recesses 422 a or 422 b are adapted to receive different sizedshanks of bone anchoring elements. With reference to FIGS. 34, 36, 46,47, a particular recess 422 a, 422 b which is in use will face outwardsor upwards towards the opening of the U-shaped recess 402 a. In thisembodiment of the insert 420, mounting of at least two different sizedbone anchoring elements 1 can be accommodated, For changing the recess422 a, 422 b which is in use, the insert 420 can be rotated around itsaxis by means of the pin 424. By utilizing the pin 424 and thecorresponding slot 423, two positions of the insert 420 are definedbased on the position of the pin 424 in one of the two legs of theU-shaped recess 402 a. By providing only two recesses 422 a and 422 b,the insert 420 is easy to clean and sterilize. Providing a pin similarto the pin 424 for rotating the insert 320 in the third embodiment isalso possible. In that case, three defined positions of the pin would beprovided, for example, by means of two short slots and a hole in theground or bottom of the longitudinal recess 302 a.

In other embodiments, a cylinder or insert having one or more than threerecesses can be provided. With the embodiments of the holder, a user cancombine screws or bone anchoring elements with different shanks to areceiving part. Hence, a modular system is provided that gives the usera wider selection of implant combinations depending on the actualclinical situation.

The bone anchoring device can be preassembled either by the manufactureror in the course of preparation of surgery or at any other time.Advantageously, the surgeon can select prior to surgery the desiredreceiving parts and bone anchoring elements according to the specificrequirements of the particular clinical application. The design of thebone anchoring device allows for selection of the appropriate boneanchoring elements in terms of diameter, length and other features ofthe anchoring section. Hence, a modular system can be provided, whichincludes receiving parts and various bone anchoring elements, which thencan be individually chosen and adapted.

In use, during surgery, a preassembled bone anchoring device includingthe receiving part body 5, the bone anchoring element 1, and the lockingring 8 in the pre-locking position, is screwed into a bone. The recess 4of the head 3 can be accessed with a screw tool through the first bore10. To correctly align the receiving part body 5 with respect to the rod6, to which it will be connected, an additional force can be exertedonto the receiving part, either manually or by application of aninstrument. Once the correct position of the rod 6 with respect to otherbone anchoring devices is also achieved, the inner screw 7 can betightened for each bone anchoring device. Since the rod 6 abuts againstthe projections 86 of the locking ring 8, the locking ring 8 is shifteddownward into the third position, which is the locking position. Whenthe locking ring 8 is moved towards the free end 17 b of the headreceiving portion 17, it compresses the head receiving portion 17,thereby locking a position of the head 3. Final tightening of the innerscrew 7 locks the rod 6 and the head 3 simultaneously.

In the pre-locking condition, the head 3 remains clamped when the innerscrew 7 is loosened. This allows further adjustments with respect topositioning of the rod 6.

Further modifications to bone anchoring devices which are compatiblewith tools according to the embodiments shown are possible. For example,the head of the bone anchoring element can have any other shape, forexample, a cylindrical shape, whereby a monoaxial bone screw isprovided, allowing rotation of the screw element with respect to thereceiving part body around a single axis. The head can also be conicallyshaped or otherwise shaped, and the internal hollow section of the headreceiving portion is adapted to correspond to this shape. In a furthermodification, the flexibility of the head receiving portion is based onproperties of the material, for example, a plastic material, and theslits may be fully or partly omitted.

The projections of the locking ring which engage the rod can haveanother shape, for example, the surface of the free end can be flat orcan be otherwise shaped. Alternatively, the projections can be omitted.

The head receiving portion can have an inclined open end, or can beotherwise asymmetric to allow for a greater angulation of the head inone direction.

The outer surface of the head receiving portion and the inner surface ofthe locking ring can have other shapes which allow for compression ofthe locking ring by means of an increasing force when the locking ringis shifted downwards relative to the receiving part body.

With respect to the tools, variations are also possible. For example,the tool can be configured such that the screw axis and the central axisof the receiving part extend perpendicular to the surface on which thetool is placed or positioned. The second holder for the receiving partbody can be movable with respect to the first holder for the boneanchoring element, hi addition, instead of a manual actuation of thetool, it may also be possible to actuate the tool by means of amechanically or electronically operated device.

While the present invention has been described in connection withcertain exemplary embodiments, it is to be understood that the inventionis not limited to the disclosed embodiments, but is instead intended tocover various modifications and equivalent arrangements included withinthe spirit and scope of the appended claims, and equivalents thereof.

What is claimed is:
 1. A tool for assembling a bone anchoring device,the bone anchoring device comprising a bone anchoring element with ahead and a shaft to be anchored in bone and a receiving part, the toolcomprising: a first holder for the bone anchoring element having aninsert configured to be inserted into a longitudinal recess of the firstholder, wherein the insert is capable of receiving the bone anchoringelement, wherein at least two recesses configured to receive differentsized bone anchoring elements are formed at an outer surface of theinsert, and wherein respective longitudinal axes of the recesses of theinsert are spaced apart from one another.
 2. The tool according to claim1, wherein the insert is rotatable in the first holder.
 3. The toolaccording to claim 1, wherein the insert has a pin.
 4. The toolaccording to claim 3, wherein the insert is rotatable in the firstholder via the pin.
 5. The tool according to claim 3, wherein the pin isprovided on one end of the insert and extends perpendicular to the atleast two recesses of the insert.
 6. The tool according to claim 3,wherein the pin fits into a slot of the first holder that extendsperpendicular to the longitudinal recess of the first holder.
 7. Thetool according to claim 1, wherein the respective longitudinal axes ofthe at least two recesses of the insert are parallel to one another. 8.The tool according to claim 1, wherein the recesses of the insert arecylinder-shaped or U-shaped.
 9. The tool according to claim 1, whereinthe recesses of the insert each extends over a whole length of theinsert.
 10. The tool according to claim 1, wherein the insert issubstantially cylindrical.
 11. The tool according to claim 1, whereintwo of the recesses of the insert are positioned circumferentially onopposite sides of the insert.
 12. An insert for a tool for assembling abone anchoring device comprising a bone anchoring element with a headand a shaft to be anchored in bone and a receiving part, the insertconfigured for insertion into a holder of the tool, the insertcomprising an elongate body with a longitudinal axis; wherein a firstrecess configured to receive a shaft of a bone anchoring element extendson a surface of the elongate body along the longitudinal axis, has afirst diameter, and is oriented towards a first radial directionrelative to the longitudinal axis; wherein a second recess configured toreceive a shaft of a bone anchoring element extends on a surface of theelongate body along the longitudinal axis, has a second diameter greaterthan the first diameter, and is oriented towards a second radialdirection relative to the longitudinal axis different than the firstradial direction.
 13. The insert according to claim 12, wherein therecesses are cylinder-shaped or U-shaped.
 14. The insert according toclaim 12, wherein the recesses each extend over a whole length of theinsert.
 15. The insert according to claim 12, wherein the body of theinsert is substantially cylindrical.
 16. The insert according to claim12, wherein the first and second recesses are positioned on oppositesides of the insert.
 17. A tool for assembling a bone anchoring device,the bone anchoring device comprising a bone anchoring element with ahead and a shaft to be anchored in a bone and a receiving part, the toolcomprising: a first holder configured to hold a bone anchoring element;a second holder configured to hold a receiving part; and an insertconfigured to be positioned in the first holder, the insert having anelongate body with a longitudinal axis, and having a first recess and asecond recess each configured to receive a shaft of a bone anchoringelement, wherein the first and second recesses each extend on a surfaceof the elongate body along the longitudinal axis, have differentdiameters, and are oriented in different radial directions relative tothe longitudinal axis.
 18. The tool according to claim 17, furthercomprising a pin on the insert.
 19. The tool according to claim 18,wherein the insert is rotatable via the pin when the insert ispositioned in the first holder of the tool.
 20. The tool according toclaim 18, wherein the pin is provided on one end of the insert andextends perpendicular to the longitudinal axis.
 21. The tool accordingto claim 18, wherein the pin is configured to fit into a slot of thefirst holder of the tool.
 22. The tool according to claim 21, whereinthe first holder has a recess for holding the insert, the slot extendsperpendicular to the recess of the first holder, and the pin of theinsert is configured to fit into the slot.
 23. The tool according toclaim 17, wherein the insert is substantially cylindrical.
 24. The toolaccording to claim 17, wherein the insert is rotatable in the firstholder.
 25. The tool according to claim 17, wherein the first and secondrecesses are positioned on opposite sides of the insert.
 26. The toolaccording to claim 17, wherein the first holder and the second holderare configured to move relative one another to assemble a bone anchoringelement that is held by the first holder with a receiving part that isheld by the second holder.
 27. The tool according to claim 17, whereinthe insert is configured for insertion into and removal from the firstholder of the tool.
 28. A method for assembling a bone anchoring devicewith a tool, the bone anchoring device comprising a bone anchoringelement with a head and a shaft to be anchored in a bone and a receivingpart, the tool comprising a first holder configured to hold a boneanchoring element, a second holder configured to hold a receiving part,and an insert configured to be positioned in the first holder, theinsert having an elongate body with a longitudinal axis, and having afirst recess and a second recess each configured to receive a shaft of abone anchoring element, wherein the first and second recesses eachextend on a surface of the elongate body along the longitudinal axis,have different diameters, and are oriented in different radialdirections relative to the longitudinal axis, the method comprising:adjusting the insert to select the first recess or the second recess,wherein the selected recess has a diameter that is greater than adiameter of the shaft of the bone anchoring element; inserting the boneanchoring element in the first holder such that the shaft is positionedin the selected recess; inserting the receiving part in the secondholder; actuating the tool from a first configuration towards a secondconfiguration to insert the head of the bone anchoring element into thereceiving part; and removing the attached bone anchoring element andreceiving part from the tool.
 29. The method according to claim 28,wherein the bone anchoring device further comprises a locking ringaround the receiving part, wherein when the receiving part is insertedin the second holder, the locking ring is in a first position relativeto the receiving part where the head of the bone anchoring element isinsertable into the receiving part, and wherein after the head of thebone anchoring element is inserted into the receiving part, the methodfurther comprises further actuating the tool towards the secondconfiguration to move the locking ring to a second position relative tothe receiving part, where the locking ring compresses a portion of thereceiving part, such that the head cannot be removed from the receivingpart and the bone anchoring element is adjustably held at a firstangular position relative to the receiving part.
 30. The methodaccording to claim 28, wherein the adjusting of the insert comprisesrotating the insert in the first holder to selectively access the firstrecess or the second recess.